棉花叶螨为害损失及防治指标研究

研究表明，棉花在苗期、蕾期和花铃期受棉花叶螨为害后，其株高、果枝数、果节数、伏桃及总成铃数和籽棉产量皆随着为害指数的升高，受影响程度加大；而影响程度又因棉花受害的生育阶段不同而异。苗期和蕾期受害影响程度显著大于花铃期。为害指数Ｘ与减产率Ｙ的关系式为：苗期Ｙ＝－０．８４８４＋５８．００４２Ｘ，蕾期Ｙ＝－２．０１０２＋５３．３１４６Ｘ，花期Ｙ＝－０．７７８９＋２６．８８３７Ｘ，据此确定，在皮棉产量１２００～１５００ｋｇ／ｈｍ２的植棉区，棉花叶螨的动态防治指标是：每１００株棉花中红叶株的为害指数为：苗期０．８４～１．０４，蕾期１．２３～１．５３，花铃期３．２８～４．０９。

Investigation of the Damage and Economic Thresholds of Spider mites to Cotton

The damage caused by cotton spider mites (Tetranychus Cinnabarinus Boisdubal) was studied in Anqing and the result showed that the height of cotton plant,number of fruit branches and cotton bolls,etc.of the injured plants was decreased in seedling and square and flower boll stages. The effect of dmage in the seddling stage and in the square stage was significantly higher than that in the flower boll stage. The reduction of boll number resulted in low yield,and the relationship of the damage index (x) and the percentage of yield decrease (y) can be expressed by a linear regrssion equations : y =-0.848 4+58.004 2 x (the seedling stage )and y =-2.010 2+53.314 6 x (the square stage)and y =-0.778 9+26.883 7 x (the folwer boll stage). The action thresholds of cotton spider mites expressed as damage index of red leaf plants in 100 cotton plants in accordance with 1200～1500kg.hm -2 yield levels were determinded as 0.84～1.04in seedling stage,1.23～1.53 in square stage ,and 3.28～4.09 in flower boll stage respectively.